Cancer is a leading cause of human death worldwide, yet there are no early detection assays available for the majority of cancer types, including breast cancer that is the second most prevalent cancer in women. Early detection of cancer is vital for successful clinical intervention, as rates of remission drop sharply at advance stages of the disease. The objective of this proposal is to develop a noninvasive serum bioassay for early detection of breast cancer using the novel glycan-binding lambodies (lamprey antibodies) we discovered. Lambodies are the unique leucine-rich repeat-based antibodies of sea lamprey, which can bind glycans with exquisite affinity and selectivity, superior to that of most lectins and mammalian antibodies, which typically bind glycans with poor affinity and/or selectivity. Human cancer cells display aberrant glycosylation patterns, with many glycan structures different from those in normal cells. The most widely used cancer biomarkers are body-fluid glycoproteins and the glycans they display can change markedly during oncogenesis. Such aberrant glycan structures could serve as diagnostic and prognostic cancer biomarkers. However, due to the poor affinity and/or selectivity for glycans of most conventional reagents, current clinical cancer diagnostic tests lack sensitivity and specificity. These biomarkers are often useful only after the disease has been diagnosed, usually at late stages when the cancer has spread to distant organs. We propose to isolate a panel of anti-breast cancer lambodies that can preferentially detect breast cancer glycoproteins compared to normal, using as probes cell-surface proteins and conditioned medium from breast cancer cell lines. These lambodies will be used develop a highly sensitive sandwich-ELISA test for detection of cancer-associated glycans in serum glycoproteins. A pilot screen will be performed with the lambodies on 40 breast cancer and 40 normal human serum samples, to determine the specificity and sensitivity of the assays. These anti-breast cancer lambodies may enable prediction of breast cancer risk, diagnosis and staging, prognosis and monitoring the response to therapy, which could have a major impact on the survival of patients.